Electric lamp filament



UNITED STATES PATENT OFFICE- CARL SEEL, OF BERLIN, GERMANY.

ELECTRICiLAIVIP FILAMENT.

SPECIFICATION forming part of Letters Patent No. 382,560, dated May 8, 1888.

' Apnncauon filed June 16, 1886. seran No. 205,340. (No model.)

To all whom t may concern:

Be it known that I, CARL SEEL, a subject of the Emperor of Germany, residing at Berlin, inv the Kingdom of Prussia, in the German Empire, have invented some new and useful Improvements in Electric Incandescent-Lamp Filaments, of which the following is a specification.

My invention relates to improvements in electric incandescent lamps, and the characterist-ic peculiarity of it is that the incandescent threads are formedof three annular layers, of which the innermost is the real carbon thread, which is saturated with mineral salts and a gum, and is thus provided with a nonconducting silicate or coating of a salt that meltsduring the carbonization. not only protects the carbon thread from burning during the carbonization and excludes the air from it, but it also gives the carbon thread a smooth surface, on which the third layer, which is necessary for the adjusting of the resistance of the lament, is deposited in a finelydividedanduniform manner. This third layer is composed of carbon', which is precipitated in a certain manner, a parafne bath being used for the purpose, as will be seen hereinafter.

them in the lamps; but in the present invenl tion the carbon threads are ready prepared before being connected and'inserted in the lamps. They are, besides, tested as to their resistance, and the current resistances are equalized when they differ. To equalize these resistances is the purpose of the present improvements. It is already known that the equalization of these differences in resistance is effected by baths of oarbonaceous gases or fluids; but in these baths there' is one great drawback-namely, that when, in consequence of a rise of temperature, the particles of carbon are deposited on the charcoal threads a constant current sets in in the baths, and as there are always particles of oxygen in'these baths all the oxygen contained in them gradually operates on the charcoal threads and detriorates their quality. The bath of solid material, which is used in this case and considered new, removes this diftculty entirely, for when the threads are steeped in such a solid This coating bath for the purpose of preparing them only those parts that are nearest to thethreads become liquid or vaporous, and from these parts of the bath alone, which are limited as much as possible, does a depositing of carbonaceous ope that closely encircles the charcoal threads,

the resistance of which has to be equalized.

In theaccoxnpanying drawings is shown in Figure 1 a vertical longitudinal section of a dashing-vessel. Fig. 2 is a vertical crosssection of the same.

The method of preparing the threads is as follows: Wood, silk, cotton, or any other vege All cur-I e table ber is steeped in vasolutionof mineral salts and a gum, consisting of a mixture of a silicate or salt, gum-senegal, and causticsoda,

andthen rolledrmlybetween warmed grooved, rollers. It is rolled, besides, inl theshape of n angle-iron, and thus combines the advantage of great resistance with thatl ofbeing a manyedged material of small diameter. edges of a charcoal thread can shed, as experience teaches, a much brighter, whiterlight `than smooth surfaces do, and therefore always the angle-iron shape is the most advanta,f :eousY v for illumination. When this operation'i's iinished, the thread is carbonized'in the usual way after any of the well-known methods. After carbonizing, the charcoal thread is placed in vessel a, a cross-section of whichis represented in Figs. 1 and 2. The cover of this vessel is made of an insulatory material, and is provided, as may be seen in the design, with metal insertion-pieces m, each two of which have two binding-screws, s s', for securing both the charcoal threads k and the conducting- The sharp IOO wires from an electric source. After. having y inserted the charcoal thread k, which has to be tested as regards resistance, in the inser-i tion-pieces, (as design shows, several threads lane or naphthaline, so full that the charcoal threads are completely immersed. The parane is then allowed to cool and stiffen, and the wires r r are connected with the electric circuit, and a resistance-meter is included in the circuit, so that the resistance can be read off at any time. The electric current that passes through the charcoal thread in this way heats it, and the parts of the paraffine close to it become liquid and those closest to it even vaporized,and then, in consequence of theheating of the particles of carbon, are deposited on the thread, and owing to this the resistance of the latter decreases gradually. The parts ofthe parafne farthest removed from the charcoal threads remain solid and form, as already mentioned, an envelope for those parts ofthe parafne that are liquid and limit the liquefying of the material as much as possible. The current of the liquid caused by the rise of the temperature is thus restricted to a minimum. When the carbon thread has been lowered to the right degree of resistance, the electric current is cut o" and the thread is ready for use. When the parafline has been made perfectly liquid by heating it, the carbon thread can be drawn out. It is then cleaned by some suitable means of the paraine particles attached to it-for instance by benzineand is then ready to be inserted in the lamp. It must therefore be observed that the actual regulating of the resistance of the carbon thread takes place in the bath, only the very smallest part of which melts. This operation admits of only the least amount of air contact, and in addition to this paraiine and naphthaline, as well as all other carburets of hydrogen that stiffen easily, offer the advantage of discharging carbon most easily.

Fig. 3 shows a perspective view of the angular carbon thread with its layers and the form of the cross-section of the carbon thread. e is the inner layer of carbon. e is the second layer, consisting of the silicate; and e is the regulating-layer of carbon gained by the effect of the electric current.

The advantage which arises from the method of preparing the thread with mineral salts and a gum is still to be explained. The composition of this mineral salt and a gum has already been mentioned. Owing to the gum-senegal being used, it completely lls up the pores of lthe thread and makes the latter exceedingly toughand gives it great powers of resistance. The silicate and the caustic soda, on the other hand, encompass the thread entirely, and when the latter is subjected to the rolling process they encircle it closely and uniformly on all sides. After being carbonized and prepared the thread will therefore consist of three layers--namely, the inner carbon layer, the annular silicate layer, and the uppermost precipitated so called regulating-layer formed by the deposition of carbon.

CARL SEEL.

Vitnesses:

TH. Hnssn, B. Roi. 

